These muscles constitute about 40% of our body weight. The muscle’s point of attachment to bones of other muscles are designated as origin or insertion. The point of origin is the point of attachment to the bone to which the muscle is anchored. The point of insertion is the point of attachment to the bone the muscle moves. Generally, the muscles are attached by tough fibrous structures called tendons. These attachments bridge one or more joints and the result of muscle contraction is movement of these joints. The body is moved primarily by muscle groups, not by individual muscles. These groups of muscles power all actions ranging from the threading of a needle to the lifting of heavy weights.